STRAIN-ENERGY AND CRITICAL THICKNESS OF HETEROEPITAXIAL INGAAS LAYERS ON GAAS SUBSTRATE

When a grown crystalline layer is as thin as one or two monolayers, the lattice constant in a grown layer is coherent with the substrate lattice even in a highly lattice-mismatched crystalline system. In this study, we calculate the strain energy in deviated bond lengths and bond angles for individual atoms by valence force field (VFF) method and find the atom position with the minimum strain energy. The critical thickness below which no dislocation occurs is derived. The thickness is thinner as compared with those predicted by previous conventional theories. However, the experimental results agree fairly well with our theoretical results.